Wiring BCM to Power with RS-25-12 - how?

Artric · 08-10-2010, 12:03 AM

I've been advised that wiring up the BCM to be powered during charging will allow the charge to grow, and not require me to do a recal in the morning. For me this is highly desirable.

I currently have my 12v PSU wired to a case fan on my grid charger and spliced into the battery pack fan. I'd like to extend that over to the BCM.

Could someone please help me figure out how I can wire in the BCM? What color wires do I need to tap into? And should I still power the fan, or will this system turn on the fan?

Also, I tried charging with the car turned on in the aux position (radio playing, etc), and the gauge didn't rise - I should have tried it in Auto-Stop, as then maybe the BCM would have power - any insight here?

I hate forced charging, if you can't tell

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Cobb · 08-10-2010, 12:46 AM

Me too, however it does wonders at reducing recals when you least expect them. I was doing a force charge the other day, ten minutes at 2 grand and it was still going. I reved to 3gs and it returned to center and the ima showed full.

Quote:

Originally Posted by Artric

II hate forced charging, if you can't tell

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Artric · 08-10-2010, 07:23 AM

I thought driving a mile at 50MPG was bad for my average, that would tear it to shreds!

Artric · 08-14-2010, 12:38 PM

Anyone have insight on this? RobertSmalls gave me some info over at Ecomodder, but since I'm too lazy to try it out right now, I'd be interested if anyone else has tried this or has any advice.

02insight · 08-14-2010, 06:39 PM

My idea would be to take 12+ from the PowerSupply, and connect that to the MCM pin (that provides 12v to MCM/BCM circuit and powers them all up), and connect the negative from the power supply to some metal ground on the chasis. Same ground that the BCM/MCM would use also.
I think this should work, but I am also new to this.., so I have been watching this thread hoping some of the senior electricity experts can chime in. I want to try it, but scared that it may short out and destroy something.

RobertSmalls · 08-14-2010, 09:12 PM

Yeah, and I'd add a diode so that when the car is on, it's not applying voltage to the power supply. I'm not sure if all that's necessary.

This is a mod that I've toyed with, but not yet tested thoroughly. Let us know how it goes.

E27006 · 08-15-2010, 07:24 AM

Why not wire via a double pole relay? When the Relay is off the BCM gets 12V from the loom, When the Relay is energised the BCM gets 12V from your Power supply

Artric · 08-15-2010, 07:28 AM

Thanks, will do. It'll probably be about a week or so before I get into it. I'm going to rewire a few things for a bit of a heftier charge. I'm considering assembling a 2A/1.75A/1.35A/1.05A/.7A/.35A manually switchable charger using three CC PSUs. Parts need to come in from Jameco.

I figure if the battery can charge at up to 50A while driving, 2A should be fine for a short period with the fan at 100%.

Also, RobertSmalls, any chance you could help me find where that ground would be for the MCM? That's really all I was seeking with this thread. I know you have some manuals and a bunch of advanced knowledge!

RobertSmalls · 08-15-2010, 09:52 AM

Chassis ground. Anywhere there's a bolt attaching something to unpainted parts of the car is fine.

2A is fine when no cells in the battery are full, but I can't shake the idea that you need a BMS that monitors the battery and shuts off or reduces the charge rate when at least one cell peaks.

Artric · 08-15-2010, 06:21 PM

I've been rethinking it today, and it will probably only max out at 1.05A, maybe 1.4A.

Most likely, I'll be buying the monitoring circuit from Mike Dabrowski that he'll be using on his chargers and building to his spec when available. If I build a 1.05A, it would only be run when the battery is completely empty, and only for a short amount of time when I need to recover some juice fast.

But the faster I destroy my battery, the faster I can try to get the balls to convert to lithium!